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Abstract:

Disclosed is a stator which can be made compact and can produce high
output, and also disclosed is a method for manufacturing the stator. A
stator comprises a split stator core provided with teeth portions and
slots, and a double coil formed of a flat type conductor, wherein the
split stator core has a first block of six slots of U, V and W phases and
a second adjoining block, the flat type conductor in the first slot of U
phase forms a first loop coil together with the flat type conductor in
the second slot of U phase, the flat type conductor in the second slot of
U phase forms a second loop coil together with the flat type conductor in
the first slot of U phase, and the second loop coil is arranged on the
inner circumference of the first loop coil.

Claims:

1. A stator comprising: a stator core including teeth portions and slots
formed between the teeth portions; and coils each being made of a flat
rectangular conductor and placed in the slots, wherein the slots include
three-phase slot blocks including a first group consisting of a U-phase
first slot, a U-phase second slot, a V-phase first slot, a V-phase second
slot, a W-phase first slot, and a W-phase second slot, which are arranged
in sequence, and a second group of the three-phase slot blocks being
arranged adjacent to the first group, the conductor placed in a U-phase
first slot of the first group and the conductor placed in a U-phase
second slot of the second group forms a first loop, the conductor placed
in a U-phase second slot of the first group and the conductor placed in a
U-phase first slot of the second group forms a second loop, the second
loop is placed on an inner circumference of the first loop, and the
conductor extending from the U-phase first slot is deformed for a lane
change in a range corresponding to two slots.

2. (canceled)

3. The stator according to claim 1, wherein a coil end portion of the
first loop is formed with a first protrusion, and a coil end portion of
the second loop is formed with a second protrusion placed on an inner
circumference of the first protrusion.

4. The stator according to claims 1, wherein one end of the first loop is
connected to one end of the second loop.

5. A method of manufacturing a stator comprising: a stator core including
teeth portions and slots formed between the teeth portions; and coils
each being made of a flat rectangular conductor and placed in the slots,
the method including: a first step of winding the conductor in a
plurality of turns in an overlapping relation to form an octagonal coil;
a second step of forming a pair of protrusions in coil end portions of
the octagonal coil; a third step of forming the coil formed with the
protrusions into a circular arc shape; and a fourth step of forming
lane-change portions in the pair of protrusions.

6. The stator manufacturing method according to claim 5, wherein the
second step includes pressing an outer surface of the octagonal coil by a
press mechanism from surrounding four directions of the fixed octagonal
coil to form the pair of protrusions.

7. The stator manufacturing method according to claim 5, wherein the
third step includes fixing the coil formed with the protrusions and then
pressing a die having a curved surface against the coil formed with the
protrusions in an axial direction to form the coil including the
protrusions into the circular arc shape.

8. The stator manufacturing method according to claim 5, wherein the
fourth step includes holding the pair of protrusions of the coil formed
in the circular arc shape by a right holding die and a left holding die
and then displacing the left holding die with respect to the right
holding die to form the lane-change portion in the pair of protrusions.

9. A stator manufacturing apparatus for manufacturing a stator
comprising: a stator core including teeth portions and slots formed
between the teeth portions; and coils each being made of a flat
rectangular conductor and placed in the slots, wherein a coil fixing part
for fixing an octagonal coil formed of the conductor wound in a plurality
of turns in an overlapping relation; and a press mechanism for pressing
an outer surface of the octagonal coil from surrounding four directions
of the fixed octagonal coil, a pair of protrusions is formed in the
octagonal coil.

10. The stator manufacturing apparatus according to claim 9, further
including: a fixing mechanism for fixing both ends of the coil formed
with the protrusions; and a die having a curved surface which is pressed
against the coil formed with the protrusions in an axial direction of the
coil, the apparatus being configured to form the coil formed with the
protrusions into a circular arc shape.

11. The stator manufacturing apparatus according to claim 10, further
including: a right holding die and a left holding die for holding the
pair of protrusions formed in the circular arc shape, and a drive
mechanism for displacing the left holding die with respect to the right
holding die, a lane-change portion is formed in each of the pair of
protrusions of the coil formed into the circular arc shape.

12. The stator according to claim 3, wherein one end of the first loop is
connected to one end of the second loop.

13. The stator manufacturing method according to claim 6, wherein the
third step includes fixing the coil formed with the protrusions and then
pressing a die having a curved surface against the coil formed with the
protrusions in an axial direction to form the coil including the
protrusions into the circular arc shape.

14. The stator manufacturing method according to claim 6, wherein the
fourth step includes holding the pair of protrusions of the coil formed
in the circular arc shape by a right holding die and a left holding die
and then displacing the left holding die with respect to the right
holding die to form the lane-change portion in the pair of protrusions.

15. The stator manufacturing method according to claim 7, wherein the
fourth step includes holding the pair of protrusions of the coil formed
in the circular arc shape by a right holding die and a left holding die
and then displacing the left holding die with respect to the right
holding die to form the lane-change portion in the pair of protrusions.

16. The stator manufacturing method according to claim 13, wherein the
fourth step includes holding the pair of protrusions of the coil formed
in the circular arc shape by a right holding die and a left holding die
and then displacing the left holding die with respect to the right
holding die to form the lane-change portion in the pair of protrusions.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a technique of improving the space
factor of a stator in order to achieve a compact and high-power motor.

BACKGROUND ART

[0002] In recent years, the needs for hybrid electric vehicles, electric
vehicles, and others have been increased. Accordingly, motors have been
studied to be used for the driving power of vehicles. However, such
motors to be mounted in the vehicles are demanded for development of high
power and downsizing. Particularly, hybrid electric vehicles are strictly
demanded for size reduction in view of the placement of a motor in an
engine room.

[0003] Therefore, various studies have been made to achieve downsizing and
high power of motors.

[0004] Patent Document 1 discloses a technique related to a conductor part
for stator frame in a multi-phase power generator.

[0005] A stator core includes outer slots. A flat rectangular conductor
provides a plane of an in-slot conductor portion to be inserted in each
slot. The flat rectangular conductor is shaped into an almost U-like form
when seen in plan view perpendicularly to the plane and a sinuous form
when seen in front view along the plane. Such flat rectangular conductor
is set in the stator core. Accordingly, a coil end of the stator can be
shortened, thereby improving the space factor.

[0007] After a flat rectangular conductor is wound in hexagon shape, a
crank-shaped portion serving as a coil end is formed by a die. Such flat
rectangular conductor is placed in a stator core to eliminate
interference between coils in the coil end, thus contributing to an
increase in the space factor of the stator and a reduction in size.

[0009] When a coil assembly wound from an inner circumferential side to an
outer circumferential side is to be placed in slots of a stator core, the
coil assembly is inserted from the coil outer circumferential side into
an outer layer side of one slot and from the coil inner circumferential
side into an inner layer side of the other slot. Accordingly, the rotary
electric machine including distributed winding coils can be manufactured
in a simplified work and also can have an improved space factor of the
slots.

[0010] Patent Document 4 discloses a technique related to a stator of a
rotary electric machine, and the rotary electric machine.

[0011] A flat rectangular conductor is wound in wave form to form a wound
coil having a plurality of phases. Split teeth are inserted from outside
and fixed in grooves in an outer annular portion of a stator core. Thus,
the stator core can be manufactured with high precision.

RELATED ART DOCUMENTS

Patent Documents

[0012] Patent Document 1: JP 3756516 B2

[0013] Patent Document 2: JP 4234749 B2

[0014] Patent Document 3: JP 2008-125212 A

[0015] Patent Document 4: JP 2009-131093 A

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

[0016] However, Patent Documents 1 to 4 may cause the following problems.

[0017] In general, a stator using a distributed winding coil can be more
developed for high power as compared with a stator using a concentrated
winding coil and hence can more easily solve the problem with cogging
torque. However, if the depth of slots in the stator cores are made
larger and the number of turns of a coil is increased to develop high
power of the stator using the distributed coil as shown in Patent
Documents 1 and 2, a problem with interference between coils occurs.

[0018] In the techniques disclosed in Patent Documents 1 and 2, there is
little clearance between adjacent coils. It therefore seems difficult to
increase the number of turns of each coil any more. In shaping a flat
rectangular conductor, the bending radius of the flat rectangular
conductor is restricted. Thus, it also seems hard to increase a
cross-sectional area of the flat rectangular conductor any more.

[0019] Consequently, the methods in Patent Documents 1 and 2 are
considered unsuitable for further development of high power.

[0020] Patent Document 3 shows only a concrete method of shaping a coil by
winding a circular wire from inner to outer circumference into a flat
shape to form a coil, clamping a portion of the coil to be inserted in a
slot, then twisting that portion. This method seems unsuitable for a flat
rectangular conductor.

[0021] Because of the use of a manner of winding the flat rectangular
conductor by stacking or overlapping the conductor on the outer
circumference, a coil end tends to become large. This seems inadequate
for downsizing of a stator.

[0022] Patent Document 4 uses a wave winding coil in distributed winding.
The wave winding coil needs weaving of a flat rectangular conductor. This
requires a complicated forming work and also a large-sized assembling
machine to stack all the flat rectangular conductors in a planar manner
and then wind the stacked flat rectangular conductors into an annular
ring shape. Accordingly, there occur problems that assembling is
difficult and cost reduction is hard to achieve.

[0023] Consequently, in view of the techniques shown in Patent Documents 1
to 4, additional devices or ideas are necessary to more reduce the size
and develop the high power of a stator.

[0024] The present invention has been made to solve the above problems and
has a purpose to provide a stator and a stator manufacturing method,
whereby enabling downsizing and development of high power.

Means of Solving the Problems

[0025] To achieve the above purpose, one aspect of the invention provides
a stator configured as below.

[0026] (1) In a stator comprising: a stator core including teeth portions
and slots formed between the teeth portions; and coils each being made of
a flat rectangular conductor and placed in the slots, the slots include
three-phase slot blocks including a first group consisting of a U-phase
first slot, a U-phase second slot, a V-phase first slot, a V-phase second
slot, a W-phase first slot, and a W-phase second slot, which are arranged
in sequence, and a second group of the three-phase slot blocks being
arranged adjacent to the first group, the conductor placed in a U-phase
first slot of the first group and the conductor placed in a U-phase
second slot of the second group forms a first loop, the conductor placed
in a U-phase second slot of the first group and the conductor placed in a
U-phase first slot of the second group forms a second loop, and the
second loop is placed on an inner circumference of the first loop.

[0027] (2) In the stator described in (1), the conductor extending out of
the U-phase first slot is deformed for lane change in a range
corresponding to two slots.

[0028] (3) In the stator described in (1) or (2), a coil end portion of
the first loop is formed with a first protrusion, and a coil end portion
of the second loop is formed with a second protrusion placed on an inner
circumference of the first protrusion.

[0029] (4) In one of the stators described in (1) to (3), one end of the
first loop is connected to one end of the second loop.

[0030] To achieve the above purpose, further, a stator manufacturing
method of another aspect of the invention is configured as below.

[0031] (5) In a method of manufacturing a stator comprising: a stator core
including teeth portions and slots formed between the teeth portions; and
coils each being made of a flat rectangular conductor and placed in the
slots, the method including: a first step of winding the conductor in a
plurality of turns in an overlapping relation to form an octagonal coil;
a second step of forming a pair of protrusions in coil end portions of
the octagonal coil; a third step of forming the coil formed with the
protrusions into a circular arc shape; and a fourth step of forming
lane-change portions in the pair of protrusions.

[0032] (6) In the stator manufacturing method described in (5), the second
step includes pressing an outer surface of the octagonal coil by a press
mechanism from surrounding four directions of the fixed octagonal coil to
form the pair of protrusions.

[0033] (7) In the stator manufacturing method described in (5) or (6), the
third step includes fixing the coil formed with the protrusions and then
pressing a die having a curved surface against the coil formed with the
protrusions in an axial direction to form the coil including the
protrusions into the circular arc shape.

[0034] (8) In one of the stator manufacturing methods described in (5) to
(7), the fourth step includes holding the pair of protrusions of the coil
formed in the circular arc shape by a right holding die and a left
holding die and then displacing the left holding die with respect to the
right holding die to form the lane-change portion in the pair of
protrusions.

[0035] Furthermore, to achieve the above purpose, a stator manufacturing
apparatus of another aspect of the invention is configured as below.

[0036] (9) In a stator manufacturing apparatus for manufacturing a stator
comprising: a stator core including teeth portions and slots formed
between the teeth portions; and coils each being made of a flat
rectangular conductor and placed in the slots, a coil fixing part for
fixing an octagonal coil formed of the conductor wound in a plurality of
turns in an overlapping relation; and a press mechanism for pressing an
outer surface of the octagonal coil from surrounding four directions of
the fixed octagonal coil, a pair of protrusions is formed in the
octagonal coil.

[0037] (10) The stator manufacturing apparatus described in (9), further
includes: a fixing mechanism for fixing both ends of the coil formed with
the protrusions; and a die having a curved surface which is pressed
against the coil formed with the protrusions in an axial direction of the
coil, the apparatus being configured to form the coil formed with the
protrusions into a circular arc shape.

[0038] (11) The stator manufacturing apparatus described in (10), further
includes: a right holding die and a left holding die for holding the pair
of protrusions formed in the circular arc shape, and a drive mechanism
for displacing the left holding die with respect to the right holding
die, the lane-change portion is formed in each of the pair of protrusions
of the coil formed into the circular arc shape.

Effects of the Invention

[0039] A stator of one aspect of the invention configured as above can
provide the following operations and effects.

[0040] The above configuration (1) provides the stator comprising: a
stator core including teeth portions and slots formed between the teeth
portions; and coils each being made of a flat rectangular conductor and
placed in the slots, wherein the slots include three-phase slot blocks
including a first group consisting of a U-phase first slot, a U-phase
second slot, a V-phase first slot, a V-phase second slot, a W-phase first
slot, and a W-phase second slot, which are arranged in sequence, and a
second group of the three-phase slot blocks being arranged adjacent to
the first group, the conductor placed in a U-phase first slot of the
first group and the conductor placed in a U-phase second slot of the
second group forms a first loop, the conductor placed in a U-phase second
slot of the first group and the conductor placed in a U-phase first slot
of the second group forms a second loop, and the second loop is placed on
an inner circumference of the first loop.

[0041] Since the flat rectangular conductor is formed into double coils
each having the first loop and the second loop, more allowance for the
lane-change portions can be sufficiently provided.

[0042] When a coil formed of a conductor in a loop shape is to be inserted
in a stator core, the conductor has to be arranged in planar pattern on
an end face of the stator core, as disclosed in Patent Documents 1 and 2.
In this case, the end face of the stator core has a limited area and thus
the number of conductor portions to increase the number of turns of each
coil could not be easily increased. When a coil is designed as a
distributed winding, concentrically winding coils will interfere with
each other and therefore each coil end portion needs a space for a
lane-change portion. Due to this lane-change portion, the width of the
coil likely becomes problematic.

[0043] To avoid the above disadvantages, the present invention provides
the double coil structure in which the second loop is formed on the inner
circumference side of the first loop, so that the end face of the stator
core can be utilized in three dimensions. As a result, the number of
turns of each coil can be increased. Even when the number of turns is
increased, the lane-change portions can prevent interference of adjacent
coils.

[0044] Since the first loop and the second loop are assembled in an
overlapping relation to form a double coil, a stator core with deep slots
can be adopted without much increasing the thickness of the coil end.
Consequently, the space factor of the stator and the demand for
downsizing can be satisfied.

[0045] The aforementioned configuration of the invention described in (2)
provides that, in the stator described in (1), the conductor extending
out of the U-phase first slot is deformed for lane change in a range
corresponding to two slots.

[0046] The lane change is necessary as long as a concentrically winding
coil is adopted for a distributed winding stator. When the concentrically
winding coil is inserted by skipping a plurality of slots as mentioned
above, interference is caused between the adjacent coils. The above
configuration is adopted to avoid such interference.

[0047] To be concrete, assuming that a flat rectangular conductor to be
inserted in slots is referred to as an in-slot conductor portion, a first
loop of the U-phase coil of which one in-slot conductor portion is
inserted in the U-phase first slot of the first group, while the other
in-slot conductor portion is inserted in the U-phase second slot of the
second group. The first loop of the V-phase coil is placed adjacent
thereto, in which one in-slot conductor portion is inserted in the
V-phase first slot of the first group and the other in-slot conductor
portion is inserted in a V-phase second slot of the second group.

[0048] The first loop of the V-phase coil described above has to be
arranged so that a portion to be inserted in the U-phase first slot of
the first group is placed under the first loop of the U-phase coil while
a portion to be inserted in the U-phase second slot of the second group
is placed above the first loop of the U-phase coil. More specifically,
the first loop and the second loop provide a double structure. One
includes, sequentially from above, a U-phase first loop, a U-phase second
loop, a V-phase first loop, and a V-phase second loop, while the other
includes, sequentially from above, a V-phase first loop, a V-phase second
loop, a U-phase first loop, and a U-phase second loop.

[0049] The lane-change portion needed as above could use only one slot
region if the flat rectangular conductor is placed in planar pattern on
the end face of the stator core. In the double coil provided in the
present invention, however, the lane-change portion can use a double
region corresponding to two slots. Accordingly, it is preferable to
prepare as wide a width as possible in view of the bending radius.

[0050] In this description, a "region corresponding to two slots"
represents the width corresponding to two slots and two teeth portions
assuming that one set of a slot and a tooth is considered as one slot
region.

[0051] This is because it is effective to increase the cross sectional
area of the rectangular conductor in order to increase the space factor.
As larger the cross sectional area, the bending radius also becomes
relatively larger. Thus, the present invention can provide a stator with
a high space factor.

[0052] The aforementioned configuration of the invention described in (3)
provides that, in the stator described in (1) or (2), a coil end portion
of the first loop is formed with a first protrusion, and a coil end
portion of the second loop is formed with a second protrusion placed on
an inner circumference of the first protrusion.

[0053] Since the above first protrusion and the second protrusion are
provided in the coil, design flexibility can be enhanced. Accordingly,
the rectangular conductor with higher flatness is more effectively used
for a coil.

[0054] With the first protrusion and the second protrusion, firstly, the
adjacent coils can be easily deformed for lane change.

[0055] In the case where a coil is wound into a hexagonal shape, its two
sides protrude like an isosceles triangle on a coil end. In this case, if
the coils are arranged so that their isosceles triangle portions pass
each other, the coils have to be spaced from each other in view of the
thickness of the conductor, needing enough width for the lane changes. In
contrast, the coils each including the first protrusion and the second
protrusion can easily avoid the interference with the adjacent coils.

[0056] For forming the first loop or the second loop, because of the
stator structure, it is further necessary to perform edgewise bending of
the conductor. However, for providing the first protrusion and the second
protrusion, the conductor is bent in a direction along a side of thinner
thickness, not in the edgewise bending direction. The conductor can
therefore be bent relatively easily with a small bending radius.

[0057] As a result, the design flexibility of the stator can be enhanced.
This can contribute to ensure easy connection with the bus bars; for
example, the terminal portions of the coil are extended outward to pass
under the first loop and the second loop without much extending the coil
end.

[0058] Enhanced design flexibility can help to simplify the process of
manufacturing the stator. This stator can provide more advantages.

[0059] The above configuration of the invention described in (4) provides
that, in one of the stators described in (1) to (3), one end of the first
loop is connected to one end of the second loop.

[0060] Since the first loops and the second loops of the coils are
connected, connection of the bus bars is not necessary after the coils
are placed in the stator core. That is, the first loop and the second
loop, which are separate, can be connected with each other in advance.
This makes it possible to reduce the number of bus bars and enhance a
work space for bus bar connection.

[0061] Bas bar connection at the coil end is necessary for electrical
connection of coils. However, if the coils are close to each other, a
connecting work may become troublesome. It is also conceivable to need
connection with the bus bars by avoiding the terminal of one of the coils
in some cases. This is not desirable.

[0062] However, since the coils with the first loops and the second loops
connected in advance are placed in the stator core, connecting portions
with the bus bars at the coil end can be reduced, which leads to
improvement of working efficiency.

[0063] Furthermore, the stator manufacturing method of another aspect of
the invention having the above features can provide the following
operations and effects.

[0064] The aforementioned configuration of the invention described in (5)
provides a method of manufacturing a stator comprising: a stator core
including teeth portions and slots formed between the teeth portions; and
coils each being made of a flat rectangular conductor and placed in the
slots, the method including: a first step of winding the conductor in a
plurality of turns in an overlapping relation to form an octagonal coil;
a second step of forming a pair of protrusions in coil end portions of
the octagonal coil; a third step of forming the coil formed with the
protrusions into a circular arc shape; and a fourth step of forming
lane-change portions in the pair of protrusions.

[0065] With the above configuration, it is possible to form the double
coil including the protrusions. Since the double coils are set in the
stator core, the stator with a high space factor and with a short coil
end can be formed.

[0066] That is, this configuration can contribute to development of high
power and size reduction of the stator.

[0067] The aforementioned configuration of the invention described in (6)
provides that, in the stator manufacturing method described in (5), the
second step includes pressing an outer surface of the octagonal coil by a
press mechanism from surrounding four directions of the fixed octagonal
coil to form the pair of protrusions.

[0068] In many cases, the octagonal coil is made of high thermal
conductive metal such as copper and aluminium which are easy to process.
Accordingly, after the octagonal coil is formed, the coil is fixed to a
base and then both sides of a portion which will become a protrusion are
pressed by the pressing mechanism, thereby forming the pair of
protrusions.

[0069] The aforementioned configuration of the invention described in (7)
provides that, in the stator manufacturing method described in (5) or
(6), the third step includes fixing the coil formed with the protrusions
and then pressing a die having a curved surface against the coil formed
with the protrusions in an axial direction to form the coil including the
protrusions into the circular arc shape.

[0070] When the die having the curved surface is pressed against the coil
formed with the protrusions, thereby deforming the coil, the coil can be
shaped into the uniform circular arc form. Because the coils having the
same shape are assembled together in overlapping relation to form a
cage-shaped coil, the overlapping portions are desired to be accurately
uniform in shape. With the use of the die, such coils can be realized.

[0071] The aforementioned configuration of the invention described in (8)
provides that, in one of the stator manufacturing methods described in
(5) to (7), the fourth step includes holding the pair of protrusions of
the coil formed in the circular arc shape by a right holding die and a
left holding die and then displacing the left holding die with respect to
the right holding die to form the lane-change portion in the pair of
protrusions.

[0072] For forming the lane-change portion, a force is applied to displace
the left holding die with respect to the right holding die, thereby
forming the lane-change portion in the pair of protrusions. The coils are
assembled in overlapping relation to form the cage-shaped coil, so that
higher accuracy of the overlapping portions than accuracy of the
lane-change portion is more advantageous. Since the right and left
holding dies hold the coil, the portions that will be overlapped in
forming the cage coil can provide more accuracy.

[0073] A stator manufacturing apparatus in another aspect of the invention
can provide the following operations and effects.

[0074] The configuration of the invention described in (9) provides a
stator manufacturing apparatus for manufacturing a stator comprising: a
stator core including teeth portions and slots formed between the teeth
portions; and coils each being made of a flat rectangular conductor and
placed in the slots, wherein a coil fixing part for fixing an octagonal
coil formed of the conductor wound in a plurality of turns in an
overlapping relation; and a press mechanism for pressing an outer surface
of the octagonal coil from surrounding four directions of the fixed
octagonal coil, a pair of protrusions is formed in the octagonal coil.

[0075] Since the apparatus includes the coil fixing part and the pressing
mechanism for pressing outer surfaces of the octagonal coil, the second
step of the stator manufacturing method described (5) and (6) can be
realized, thus deforming the outer shape of the octagonal coil.

[0076] To form the stator described in (3), the first protrusion has to be
formed in the coil end portion the first loop and the second protrusion
has to be formed in the coil end portion the second loop. With the above
configuration, the first protrusion or the second protrusion can be
easily formed.

[0077] The aforementioned configuration of the invention described in (10)
provides that the stator manufacturing apparatus described in (9) further
includes: a fixing mechanism for fixing both ends of the coil formed with
the protrusions; and a die having a curved surface which is pressed
against the coil formed with the protrusions in an axial direction of the
coil, the apparatus being configured to form the coil formed with the
protrusions into a circular arc shape.

[0078] With the use of the die having the curved surface, the coil formed
with the protrusions can be shaped into a circular arc form. Thus, the
third step described in (7) can be realized.

[0079] The aforementioned configuration of the invention described in (11)
provides that, the stator manufacturing apparatus described in (10)
further includes: a right holding die and a left holding die for holding
the pair of protrusions formed in the circular arc shape, and a drive
mechanism for displacing the left holding die with respect to the right
holding die, the lane-change portion is formed in each of the pair of
protrusions of the coil formed into the circular arc shape.

[0080] For assembling the coils each formed in the circular-arc shape in
an overlapping relation, it is necessary to avoid interference between
adjacent coils. Therefore, the lane-change portions are formed in each
coil, so that the stator with short coil ends can be formed as with the
invention described in (5). Further, a force is applied with use of the
drive mechanism and the right and left holding dies, so that the
lane-change portions can be formed one each at the corresponding
positions of the upper and lower coil end portions of the circular-arc
coil. With this configuration, the fourth step described in (8) can be
realized.

[0102]FIG. 3 is a top view of the double coil, seen from above in FIG. 2.

[0103] A stator 100 includes double coils 30, a split stator core SC, an
outer ring 50, and a terminal stand 55. The double coils 30 in FIG. 1 are
connected with bus bars BB and coil end portions of the coils 30 are
tilted.

[0104] Each double coil 30 includes a first loop coil 10 and a second loop
coil 20 as shown in FIG. 2. Each of the first loop coil 10 and the second
loop coil 20 is formed of a wound flat rectangular conductor (conductor
wire) D.

[0105] This conductor D is made of a metal wire having a rectangular cross
section and coated with insulating resin. The metal wire is made of high
insulating metal and the insulating resin is high insulating resin such
as enamel and PPS.

[0106] The first loop coil 10 includes a first terminal portion TR11a and
a second terminal portion TR11b, and also a lead-side protrusion PR11 and
a non-lead-side protrusion PF11. On both sides of the lead-side
protrusion PR11, a lead-side right recess DRR11 and a lead-side left
recess DLR11 are formed. On both sides of the non-lead-side protrusion
PF11, a non-lead-side right recess DRF11 and a non-lead-side left recess
DLF11 are formed. Further, the lead-side protrusion PR11 is formed with a
lead-side lane-change portion LCR11 and the non-lead-side protrusion PF11
is formed with a non-lead-side lane-change portion LCF11.

[0107] The first loop coil 10 also includes a first in-slot conductor
portion SS11a and a second in-slot conductor portion SS11b which are to
be inserted in slots SCS of the stator core SC.

[0108] The second loop coil 20 includes, as with the first loop coil 10, a
first terminal portion TR12a and a second terminal portion TR12b.
Further, a lead-side protrusion PR12 and a non-lead-side protrusion PF12
are formed. On both sides of the lead-side protrusion PR12, a lead-side
right recess DRR12 and a lead-side left recess DLR12 are formed. On both
sides of the non-lead-side protrusion PF12, a non-lead-side right recess
DRF12 and a non-lead-side left recess DLF12 are formed. The lead-side
protrusion PR12 is formed with a lead-side lane-change portion LCR12 and
the non-lead-side protrusion PF12 is formed with a non-lead-side
lane-change portion LCF 12.

[0109] The second loop coil 20 also includes a first in-slot conductor
portion SS12a and a second in-slot conductor portion SS12b.

[0110] The double coil 30 is formed by placing the second loop coil 20 on
the inner circumferential side of the first loop coil 10 in overlapping
relation.

[0111] The split stator core SC consists of twenty-four pieces 41 each of
which is made of laminated electromagnetic steel plates and arranged in a
cylindrical form, and the outer ring 50 is fit on the stator core SC to
hold the double coils 30.

[0112] The stator core SC is provided, on its inner circumferential side,
the slots SCS and the teeth portions 43 alternately arranged. Each piece
41 has a shape divided in the bottoms of the slots SCS to include two
teeth portions 43.

[0113] The outer ring 50 is a cylindrical metal body formed with such a
size that an inner periphery thereof conforms to an outer periphery of
the stator core SC. The outer ring 50 is mounted around the stator core
SC by shrink fitting. Accordingly, the inner periphery of the outer ring
50 is designed to be slightly smaller than the outer periphery of the
stator core SC.

[0114] The terminal stand 55 is a connection port to be connected with an
external connector not shown for the purpose of e.g. supplying electric
power to the double coils 30 of the stator 100 after having been
electrically connected, from a power source such as a secondary battery.
In the first embodiment, the stator is configured for three phases and
hence three connection ports are provided.

[0115] A method of forming the coil in the first embodiment will be
explained below.

[0116]FIG. 4 is a top view of a coil protrusion forming jig. FIG. 5 is a
top view showing a forming state using the coil protrusion forming jig.

[0117] Firstly, an octagonal initial coil C1 is formed by winding a flat
rectangular conductor D by edge-wise bending. The initial coil C1 is set
on a center holder J11 of the coil protrusion forming jig J1. The jig J1
corresponds to a coil fixing part. The center holder J11 and a protrusion
guide J12 are placed in combination. As shown in FIG. 4, the initial coil
C1 is put so as to surround the center holder J11 and the protrusion
guide J12.

[0118] The coil protrusion forming jig J1 includes press jigs J13
corresponding to a press mechanism to shape the initial coil C1 to have
the lead-side right recess DRR11 through the non-lead-side left recess
DLF11 of the first loop coil 10 or the lead-side right recess DRR12
through the non-lead-side left recess DLF12 of the second loop coil 20.

[0119] While the initial coil C1 is set on the center holder J11 and the
protrusion guide J12, a rod J14 of each press jig J13 is moved ahead,
thereby forming recesses as shown in FIG. 5. As a result, the initial
coil C1 is shaped into a protrusion-including coil C2 formed with the
lead-side protrusion PR11 and the non-lead-side protrusion PF11 of the
first loop coil 10 or the lead-side protrusion PR12 and the non-lead-side
protrusion PF12 of the second loop coil 20.

[0120] It is to be noted that the initial coil C1 for the first loop coil
10 and the initial coil C1 for the second loop coil 20 are actually
different in circumferential length but are described herein as being
equal for convenience.

[0121] Actual shapes of the center holder J11 and the protrusion guide J12
of the protrusion forming jig J1 are different between the initial coil
C1 for the first loop coil 10 and the initial coil C1 for the second loop
coil 20. Accordingly, it is necessary to provide separate jigs
respectively adapted to the different initial coils C1 or provide a
variable guide mechanism.

[0122] Successively, the protrusion including coil C2 shaped by forming
the protrusions in the initial coil C1 has to be subjected to a step of
deforming the coil C2 into a circular arc shape. FIG. 6 is a side view of
a curve deforming jig. FIG. 7 shows a state where the coil is shaped by
use of the curve deforming jig.

[0123] A curve deforming jig J2 includes a fixed die J21, a movable die
J22, and a shaft J23.

[0124] The fixed die J21 has a curved surface necessary to deform the
first loop coil 10 and the second loop coil 20 with a radius curvature
required for placement thereof in the stator 100. The movable die J22
also has a similar curved surface and is arranged to be movable along the
shaft J23 in a direction toward the fixed die J21.

[0125] The movable die J22 includes four components; a center holding
member J22c corresponding to a fixing mechanism to press the protrusion
including coil C2, a first curve forming die J22a and a second curve
forming die J22b for deforming the protrusion including coil C2, and a
die base J22d.

[0126] The first and second curve forming dies J22a and J22b are equal in
radius curvature to the curved surface of the fixed die J21 (strictly
speaking, the fixed die J21 and the thickness of a curve including coil
C3 corresponds to the radius curvature of the second curve forming die
J22b), enabling bending of the protrusion including coil C2.

[0127] While the coil C2 is set in the curve deforming jig J2, the coil C2
is held by the center holding member J22c, the first and second curve
forming dies J22a and J22b fixed to the die base J22d are given thrust to
move together with the die base J22d toward the fixed die J21, thereby
deforming the coil C2. As a result, the coil C2 is deformed into a curve
including coil C3 as shown in FIG. 7.

[0128] Further, an explanation is given to a step of forming, in the coil
C3, a lead-side lane-change portion LCR11 and a non-lead-side lane-change
portion LCF11 of the first loop coil 10 and a lead-side lane-change
portion LCR12 and a non-lead-side lane-change portion LCF12 of the second
loop coil 20.

[0132] The fixing base J31 is placed on a base J35. The fixing base J31
and the fixing chuck J32 are movable in a direction that approaches the
fixing base J31 to hold one end of the curve including coil C3.

[0133] The movable chuck J33 and the movable base J34 are held on a slide
base J38 by a shaft 36 passing therethrough. The slide base J38 fixed to
a slide guide J37 has a drive mechanism to be movable rightward and
leftward in FIG. 8 relative to the fixing base J31. The movable chuck J33
and the movable base J34 have a drive mechanism to be movable upward and
downward in FIG. 8 relative to the slide base J38. The movable chuck J33
and the movable base J34 are also arranged to hold the other end of the
curve including coil C3.

[0134] The curve including coil C3 is held in such a state as shown in
FIG. 8 by the lane-change forming jig J3. When the slide base J38 is
moved ahead and simultaneously the movable chuck J33 and the movable base
J34 clamping the other end of the coil C3 are moved down, a lane-change
including coil C4 is formed as shown in FIG. 9.

[0135] This coil C4 is the first loop coil 10 or the second loop coil 20
shown in FIG. 2 and in a state where it can be installed in the split
stator core SC.

[0136] The first loop coil 10 or the second loop coil 20 formed as above
are stacked or assembled together to constitute the double coil 30.

[0137] The double coil 30 includes three zones as shown in FIG. 3, that
is, an inner-circumferential zone 31, an outer-circumferential zone 32,
and a protruding lane-change zone 33. The lane-change zone 33 is defined
as a generic term of a range corresponding to the lead-side lane-change
portion LCR11 of the lead-side protrusion PR11 or the non-lead-side
lane-change portion LCF11 of the non-lead-side protrusion PF11 in the
first loop coil 10 or the lead-side lane-change portion LCR12 of the
lead-side protrusion PR12 or the non-lead-side lane-change portion LCF12
of the non-lead-side protrusion PF12 in the second loop coil 20.

[0138] After the those double coils 30 are stacked or assembled in
overlapping relation in a cage form, forming a cage-shaped coil (cage
coil) CB, the split stator core SC is inserted therein.

[0139] FIG. 10 is a schematic perspective view of the stacked double
coils. It is to be noted that the first terminal portion TR11a, the
second terminal portion TR11b, the first terminal portion TR12a, and the
second terminal portion TR12b are omitted for convenience of explanation.

[0140] A double coil 30A and a double coil 30B are double coils 30 having
the same shape and are arranged so that respective lane-change zones 33
are adjacent as shown in FIG. 10. Accordingly, the inner circumferential
zone 31 of the double coil 30B is located under the lane-change zone 33
of the double coil 30A.

[0141] On the other hand, the inner circumferential zone 31 of the double
coil 30A is located under the lane-change zone 33 of the double coil 30B.

[0142] It is to be noted that positioning jigs J5 are illustrated behind
the double coils 30A and 30B. The positioning jigs J5 serve to position
the double coils 30.

[0143] FIG. 11 is a perspective view showing a state where a piece is to
be inserted in the cage coil. In this figure, as in FIG. 10, the first
terminal portion TR11a, the second terminal portion TR11b, the first
terminal portion TR12a, and the second terminal portion TR12b are omitted
for convenience of explanation.

[0144]FIG. 12 is a schematic view showing the cage coil in which the
piece is inserted. The pieces in FIG. 12 appear as only upper surfaces
for explanation.

[0145] The cage coil CB is constituted of the double coils 30 sequentially
stacked as shown in FIG. 10. This cage coil CB includes twenty-four sets
of the double coils 30. The pieces 41 are inserted therein from outside,
completing the cylindrical split stator core SC.

[0146] Finally, the outer ring 50 is shrink-fitted on the outer periphery
of the stator core SC as shown in FIG. 1. The stator 100 is thus
completed.

[0147] In the cage coil CB, as shown in FIG. 12, the first terminal
portion TR11a, the second terminal portion TR11b, the first terminal
portion TR12a, and the second terminal portion TR12b are formed to
protrude. After shrink-fitting of the outer ring 50, those terminal
portions TR11a, TR11b, TR12a, and TR12b are bent outward and connected
with bus bars BB into a state shown in FIG. 1.

[0148]FIG. 13 is a schematic plan view showing first loops of U-phase
coils in the stator core.

[0149]FIG. 14 is a schematic plan view showing second loops of the
U-phase coils in the stator core.

[0150] Assuming that a set of a U phase, a V phase, and a W phase is
referred to as one block, the stator 100 consists of eight blocks. A
first block B1 includes six slots, i.e., a U-phase first slot U1B1, a
U-phase second slot U2B1, a V-phase first slot V1B1, a V-phase second
slot V2B1, a W-phase first slot W1B1, and a W-phase second slot W2B1.

[0151] A second block B2 includes six slots, i.e., a U-phase first slot
U1B2, a U-phase second slot U2B2, a V-phase first slot V1B2, a V-phase
second slot V2B2, a W-phase first slot W1B2, and a W-phase second slot
W2B2.

[0152] The first loop coil 10 of the double coil 30 is arranged as shown
in FIG. 13 so that a second in-slot conductor portion SS11b is inserted
in the U-phase first slot U1B1 and a first in-slot conductor portion
SS11a is inserted in the U-phase second slot U2B2.

[0153] On the other hand, the second loop coil 20 of the double coil 30 is
arranged as shown in FIG. 14 so that a second in-slot conductor portion
SS12b is inserted in the U-phase second slot U2B1 and a first in-slot
conductor portion SS12a is inserted in the U-phase first slot U1B2.

[0154] The stator 100 in the first embodiment is configured as above and
hence can exhibit the following operations and advantages.

[0155] Firstly, the stator 100 can develop high power and achieve
downsizing.

[0156] The stator 100 in the first embodiment includes the split stator
core SC including the teeth portions 43 and the slots SCS formed between
the teeth portions 43, and the double coils 30 each being made of the
flat rectangular conductor D and arranged in the slots SCS. The slots SCS
include three-phase slot blocks including the first block B1 consisting
of the U-phase first slot U1B1, the U-phase second slot U2B1, the V-phase
first slot V1B1, the V-phase second slot V2B1, the W-phase first slot
W1B1, and the W-phase second slot W2B1, which are arranged in sequence.
Adjacent to the first block B1, the second block B2 of the three-phase
slot blocks is provided. The conductor D in the first slot U1B1 of the
first block B1 and the conductor D in the U-phase slot U2B2 of the second
block B2 form the first loop coil 10. The conductor D in the U-phase
second slot U2B1 of the first block B1 and the conductor D in the U-phase
first slot U1B2 of the second block B2 form the second loop coil 20. The
second loop coil 20 is placed in the inner circumference of the first
loop coil 10.

[0157] Accordingly, when the stator 100 is to be formed in a distributed
winding manner using concentrically wound coils formed as the double
coils 30, the range to be used for the lane-change zone 33 can be
ensured.

[0158] As the number of turns of each double coil 30 increases, or as the
width of the flat rectangular conductor D used for the double coil 30 is
thicker, the protruding lane-change zone 33 of the double coil 30 tends
to be hard to form. This may become an obstacle to increasing the space
factor of the stator 100 and enhancing output power. However, each double
coil 30 is configured by stacking the first loop coil 10 and the second
loop coil 20, so that the range to be used for the protruding lane-change
zone 33 can be increased.

[0159] Accordingly, the space factor of the stator 100 can be increased,
contributing to development of high output power.

[0160] To be concrete, the range for forming the lane-change zone 33 is
determined to correspond to two slots as shown in FIGS. 13 and 14. It is
therefore possible to increase the number of turns of the first loop coil
10 and the second loop coil 20 in the double coil 30 or increase the
thickness of the flat rectangular conductor D.

[0161] In view of the minimum bending radius of the flat rectangular
conductor D, damage on an insulating layer provided around the flat
rectangular conductor D, and other problems, it is not preferable to bend
a bending portion of the protruding lane-change zone 33 at an acute
angle. Depending on which range is available for the protruding
lane-change zone 33, the number of turns of the first loop coil 10 and
the second loop coil 20 or the thickness of the flat rectangular
conductor D are determined.

[0162] However, for development of high output power, it is essential to
increase the thickness of the flat rectangular conductor D and the number
of turns. Thus, it is highly advantageous to use a range corresponding to
two slots (a two-slot range) for the protruding lane-change zone 33.

[0163] In the case where a single coil is used in a stator, a lane change
can only use a range corresponding to one slot at most. In contrast, the
stator 100 in the first embodiment using the double coils 30 allows a
range corresponding to two slots to be used for forming one protruding
lane-change zone 33. This configuration contributes to development of
high output power of the stator 100 and also enhancement of design
flexibility.

[0164] Since the first loop coil 10 and the second loop coil 20 are
stacked to form the double coil 30, the space for the lane-change zone 33
is ensured as mentioned above. Thus, there is no need to elongate the
coil end in the axial direction of the stator 100. This contributes to
shortening of the coil end CE shown in FIG. 1.

[0165] The first terminal portion TR11a, the second terminal portion
TR11b, the first terminal portion TR12a, and the second terminal portion
TR12b and the bus bars BB connected to the terminal portions are
connected by welding or others and then tilted radially outward as shown
in FIG. 1. Consequently, the extension of the coil end CE can be
minimized.

[0166] Since the coil end CE of the stator 100 is not made larger beyond
necessity, the demand for downsizing can be satisfied.

[0167] Furthermore, the first loop coil 10 is provided with the lead-side
protrusion PR11 and the non-lead-side protrusion PF11, the second loop
coil 20 is provided with the lead-side protrusion PR12 and the
non-lead-side protrusion PF12. This makes it possible to prevent the
interference between adjacent coils and minimize the length of the coil
end CE.

[0168] Patent Document 2 and others adopt a configuration that a first
loop coil 10 and a second loop coil 20 are formed in hexagonal shape so
that one apex of the hexagonal shape is located in a coil end. However,
such configuration likely results in a large coil end.

[0169] This is because a flat rectangular conductor D has to be bent
obliquely in the coil end portion to detour around the adjacent coils,
the distance between the adjacent coils is likely to be longer unless the
angle of the one apex of the hexagonal shape protruding in the coil end
is made obtuse.

[0170] On the other hand, in the case where a protrusion is provided as in
the first loop coil 10 and the second loop coil 20 in the first
embodiment, the flat rectangular conductor D can avoid interference in
three dimensions.

[0171] To be concrete, the inner circumferential zone 31 or the outer
circumferential zone 32 is placed under the lane-change zone 33, so that
the lane-change zones 33 are arranged in the coil end CE. This can
contribute to shortening of the coil end CE.

[0172] In the first embodiment, the double coils 30 having the same shape
are stacked or assembled to form the cage coil CB. Accordingly, a
manufacturing cost of components can be reduced and an assembling process
can be made simple.

[0173] A second embodiment of the present invention will be explained
below.

Second Embodiment

[0174] A stator 100 in the second embodiment is almost identical in
structure to the stator 100 in the first embodiment, excepting a method
of forming a double coil 30 in a slightly different manner from in the
first embodiment. This method is explained below.

[0175]FIG. 15 is a partial perspective view of a coil end portion of a
double coil in the second embodiment. FIG. 16 is a partial perspective
view of a stator.

[0176] The double coil 30 used in the second embodiment includes a first
loop coil 10 and a second loop coil 20 connected with a connecting
portion CR shown in FIG. 15 without using a bus bar BB. That is, the
first terminal portion TR11a of the first loop coil 10 is connected to
the second terminal portion TR12b of the second loop coil 20 in the first
embodiment shown in FIG. 2, forming the connecting portion CR as shown in
FIG. 15.

[0177] The connecting portion CR passes under lead-side protrusions PR11
and goes across side surfaces of lead-side protrusions PR12 to connect
the inner circumferential side to the outer circumferential side. As
shown in FIG. 15, a terminal portion of the second loop coil 20 is
elongated to form the connecting portion CR which is connected to the
first loop coil 10 on the outer circumference side of the stator 100.

[0178] Accordingly, in each double coil 30, two parts, i.e., the second
terminal portion TR11b of the first loop coil 10 and the first terminal
portion TR12a of the second loop coil 20 protrude on the coil end CE
side.

[0179] To form a cage coil CB from the double coils 30, forty-eight double
coils are prepared in each of which the first terminal portion TR11a is
connected to the second terminal portion TR12b to form the connecting
portion CR. However, the second terminal portion TR11b and the first
terminal portion TR12a need to be different in shape for the reason
mentioned below. In practice, therefore, twenty-four double coils 30 each
having a long second terminal portion TR11b and twenty-four double coils
30 each having long first terminal portion TR12a are prepared.

[0180] The first terminal portion TR12a extending from the outer
circumferential side of the U-phase first slot U1B2 of the second block
B2 as shown in FIG. 16 is connected to the first terminal portion TR12a
extending from the outer circumferential side of the U-phase first slot
U1B3 of the third block B3. This is referred to as a first
outer-circumferential connecting portion CR01. That is, adjacent double
coils 30 of the same phase are connected to each other. In FIG. 16, the
U-phase first coil 30U1 is connected to the U-phase second coil 30U2.

[0181] Although a second terminal portion TR11b placed on the inner
circumferential side is not illustrated, it is similarly connected to the
second terminal portion TR11b of an adjacent coil of the same phase. In
the case of FIG. 16, it is connected to a U-phase eighth coil 30U8 not
shown, forming a first inner-circumferential connecting portion CR11.

[0182] Similarly, a second terminal portion TR11b of a V-phase first coil
30V1 and a second terminal portion TR11b of a V-phase second coil 30V2
placed on the inner circumferential side in the stator 100 are connected
to form a second inner-circumferential side connecting portion CR12. A
first terminal portion TR12a of the V-phase second coil 30V2 and a first
terminal portion TR12a of a V-phase third coil 30V3 are connected to form
a second outer-circumferential connecting portion CR02. In this way, the
second terminal portions TR11b placed on the inner circumferential side
of the stator 100 are connected to each other to form
inner-circumferential connecting portions CRI and the first terminal
portions TR12a placed on the outer circumferential side of the stator 100
are connected to each other to form outer-circumferential connecting
portions CRO, thereby electrically connecting the double coils 30 in the
stator 100. Thus, an electric circuit of the stator 100 is established.

[0183] According to the positions of the double coils 30, as mentioned
above, the double coils 30 need to include a shape having the second
terminal portion TR11b and having the first terminal portion TR12a both
being simply extending upward and a shape having the second terminal
portion TR11b and the first terminal portion TR12a both extending up to
the terminal portions TR11b and TR12a of a coil of an adjacent phase. The
double coils 30 are therefore prepared in two patterns.

[0184] Connection between the second terminal portions TR11b and
connection between the first terminal portions TR12a of coils of adjacent
phases may be conducted by use of bus bars BB.

[0185] In the stator 100 in the second embodiment having the above
configuration, connecting of the first loop coil 10 and the second loop
coil 20 is not conducted after the double coils 30 are combined with the
split stator core SC in the stator 100. The stator 100 is therefore easy
to produce.

[0186] A reduction in the number of connecting steps in the coil end CE
can ensure a work space and other advantages, contributing to an increase
in yield.

[0187] It is however necessary to alternately assemble the double coils 30
of two patterns, differently from the first embodiment, resulting in
somewhat complicated assembling process. However, the coil end of the
stator 100 in the second embodiment can be shorter than that of the
stator 100 in the first embodiment. Further, the structure shown in FIGS.
15 and 16 needs no bus bar BB, which contributes to a reduction in the
number of components.

[0188] A third embodiment of the present invention will be explained
below.

Third Embodiment

[0189] A stator 100 in the third embodiment is almost identical in
structure to the stator 100 in the first embodiment, excepting the shape
of the double coils 30 and a connecting method of the double coils 30,
which will be explained below. FIG. 17 is a partial perspective view of a
coil end portion of stacked or assembled double coils in the third
embodiment, seen from the inner circumferential side. FIG. 18 is a
partial perspective view of the coil end portion of the double coils seen
from the outer circumferential side. The double coils 30 in the third
embodiment are shown in the form of a cage coil CB in which pieces 41 of
a split stator core SC are inserted. The basic shape of the double coils
30 is almost the same as the double coils 30 in the second embodiment, in
which the first loop coils 10 and the second loop coils 20 are connected.

[0190] However, as shown in FIG. 18, a U-phase first coil 30U1, a V-phase
first coil 30V1, and a W-phase first coil 30W1 are different in shape
from a U-phase second coil 30U2 and a V-phase second coil 30V2.

[0191] Each double coil 30 is arranged so that a second terminal portion
TR11b placed on the inner circumferential side of the stator 100 as shown
in FIG. 17 passes under a lead-side protrusion PR12 of the second loop
coil 20 to extend to the outer circumferential side.

[0192] The double coils 30 are stacked or assembled into a cage coil CB. A
first outer-circumferential connecting portion CRO1 to a fourth
outer-circumferential connecting portion CRO4 are formed on the outer
circumferential side of the stator 100.

[0193] Since the outer-circumferential connecting portions CRO are formed
on the outer circumferential side of the stator 100 in the third
embodiment as above, thereby enabling electrical connection of the cage
coil CB, shortening of the coil end can be achieved.

[0194] There is no need to form inner-circumferential connecting portions
CRI, unlike the stator 100 in the second embodiment. Accordingly, the
stator 100 in the third embodiment includes no protrusion on the inner
circumferential side and thus does not interfere with a rotor not shown.

[0195] Even when the outer-circumferential connecting portions CRO project
to a place corresponding to the outer circumferential portion of the
split stator core SC, the connecting portions CRO interfere with nothing
Accordingly, this configuration can enhance design flexibility, even
though it needs somewhat complicated winding of a flat rectangular
conductor D.

[0196] The present invention is explained in the above embodiments but is
not limited thereto. The present invention may be embodied in other
specific forms without departing from the scope of the essential
characteristics thereof.

[0197] For instance, in the coil end CE in the first embodiment, the first
terminal portion TR11a, the second terminal portion TR11b, the first
terminal portion TR12a, and the second terminal portion TR12b may be
connected as in the second and third embodiments without using the bus
bars BB.

[0198] Further, the number of turns of each of the first loop coil 10 and
the double coil 30 and the thickness of the flat rectangular conductor D
are determined according to design requirements. For instance, the number
of turns and the cross-sectional area of the flat rectangular conductor D
may be increased or decreased.

[0199] Any connecting pattern of the first terminal portion TR11a, the
second terminal portion TR11b, the first terminal portion TR12a, and the
second terminal portion TR12b in the coil end CE may be adopted other
than the connecting patterns explained in the first to third embodiments.
Any other connecting patterns may be adopted as long as the double coils
30 can be efficiently utilized.